Other "vi"-style extensions do little more than offer some convenient key bindings. Pentadactyl allows you to create key bindings or commands that invoke arbitrary javascript to modify the current page or to access Firefox (or extension) functionality. You can attach commands to event handlers so they'll run when certain pages are opened/loaded/closed/etc. You can use CSS to style the FF GUI and websites. Use CSS selectors or XPath to define extended hint modes and attach your own Javascript functions to them. Call external commands. And if you want, you can do it all interactively, from the Pentadactyl command line.

Admittedly, Pentadactyl isn't perfect. It has a few bugs and lacks some functionality that would be really useful. But it's still the most useful extension out there — for any browser. Probably more useful than all the others put together. If the upcoming architectural changes to Firefox destroy or cripple Pentadactyl, I'll be switching to Pale Moon in order to continue using it.

Realistically, the single reason I still use Firefox. Highly recommended for vimfolk. As others have said, might have to build yourself to get a version compatible with FF 34. Perhaps we ought to donate more to the dev!

Pentadactyl is an essential part of my work (and play) on the web. No other vim-alike plugin for FF or Chrome even comes close. I use it for hours every single day and have barely scratched the surface of what it's capable of. I am currently trying to donate $20 through PayPal since I would gladly pay that for a supported commercial version. Yes, it's that good. Unfortunately the donation button on this site doesn't work for me -- it contacts PayPal and fails with 'invalid data' (how unhelpfully opaque). If anyone is reading this who can repair the donation button, please do!

To Kris and the others who've worked on Pentadactyl over the years, a hearty thank you! You've made this nerd's life better.

Now that the dev seems to have stopped updating this add-on, I totally regret not sending him/them some money to encourage their good work. If they update for FF34, I'll be sure to send them some encouragement!

I echo what Jason said September 19, 2014, except I have maye 3 key reasons for sticking with the Fox.

Was disappointed to see that this addon was incompatible with the latest version of firefox, but was pleased to see the offer of nightly builds for newer versions. They work great! Must have addon for a wonderful mouse-free browsing experience

Outstanding add-on. I use it for my work browser (you know, the one not having Facebook and Twitter tabs), having multiple tabs to issue tracking apps, configuration management sites, etc. Pentadactyl is a real productivity booster. One can very quickly find one particular open (or previously open, now closed) tab by just entering a simple keystroke and keyword. Searches are too simple. It looks cool too.

Totally blasted my GUI into oblivion, no easily accessible settings. I thought it would be useful however reality proven otherwise. Apparently it's usable only for a very specific population, not for general users.